Typically, communication management unit (CMU)/communication management function (CMF) datalink systems select an appropriate air-ground subnetwork to communicate downlink messages based on a configured air-ground subnetwork preference. The subnetwork preference may define subnetwork preferences in a particular geographic region and may be based on a message type basis in an AOC database. For example, the subnetwork preference may be implemented as a cost based routing preference logic associated with a region. In some regions, however, a different subnetwork preference may be desired when the vehicle is on the ground as compared to when the vehicle is in the air. Further, in certain regions, some networks may be available at lower altitudes that have different capabilities than the networks that are available at higher altitudes.